The island of Taiwan is a product of the oblique collision between the Luzon arc and the Chinese continent margin. The present-day collision process of Taiwan is vigorous, as revealed by the high seismic activity and the active surface deformation. The deformations generated in this convergent system have been debated from a variety of geological and geophysical observations. In this study, we applied the InSAR technique to determine the coseismic deformation of the central Taiwan area associated with the 1999 Chichi earthquake. The M w 7.6, Chichi, Taiwan earthquake of 20 September 1999 produced reverse slip with left-lateral component along an 80 km-long surface rupture, the Chelungpu fault. Four ERS2-SAR images acquired before and after the event allow determination of the co-seismic surface displacement. This analysis reveals minor subsidence in the footwall block of the Chelungpu fault, with a maximum displacement of about 25 cm along the radar line of sight.

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